Generally (unless you’re in an ENM arrangement) most of us enter into our romantic relationships with some fair assumptions about loyalty, fidelity and betrayal.
There are indeed some clear red lines we can all agree on. If you’re in a monogamous relationship and your partner has sex with someone else, without your knowledge, we know that’s cheating. Up to that point, knowing where the line is and when it has been crossed is usually subjective. Knowing where each other draws that line is a conversation that often only happens when something comes to light and by that point, one of you is hurt.
Don’t assume that you both think the same. What you categorise as emotional cheating might look like harmless fun to your partner. You might find certain types of conversation, texts, meeting up as an unacceptable level of intimacy with another, but it might not feel like that to your partner.
Bringing to light each other’s boundaries proactively not only defends against future ruptures but is the type of conversation that deepens your emotional intimacy with each other, leading to better understanding and a strengthening of trust. These terms are unique to your relationship and benefit from being explicitly agreed.
Begin by considering for yourself where your expectations of your partner are, then reflect on whether you would expect the same of yourself. Understanding your own boundaries is an important piece of self-knowledge and a good foundation to having this conversation together.